Most of the practically important implantable electromedical devices are adapted for applying electrical pulses to bodily tissue by means of appropriately positioned electrodes. For implementing this function, in the housing of the device, electronic/electrical functional units are provided for generating the pulses and for suitably controlling the pulse generation, whereas on the outer surface of the device, electrodes or contacts for at least one electrode lead are provided, which lead then has the electrodes for applying the pulses to the tissue arranged in its distal end portion. The electronic/electrical functional units within the device are to be connected to the outer electrodes or lead contacts in an adequate manner, which ensures an absolutely and long-term reliable function even under the specific conditions of the implanted state of the device.
This is solved by so-called feedthroughs, which have been the subject of numerous and largely different developments. In many such feedthroughs, terminal pins are provided, which extend from a printed circuit board or a similar carrier of electrical leads to outside the housing of the functional units. These terminal pins and, more specifically, their electrical and mechanical connection to the carrier, have to satisfy highest standards with regard to their reliability even under the influence of bodily fluids.
Therefore, terminal pins have been developed and used, which consist of a noble metal (e.g., platinum) and which can be connected to the lead carrier in a soft solder process in an easy and reliable way, but which are very costly. Besides such terminal pins, multi-part configurations are available, which comprise a terminal pin body and a soft-solderable supplement (pad) made from different materials.
U.S. Pat. No. 8,648,255 discloses terminal pins that include a refractory metal partially welded to a terminal plug of a dissimilar metal incorporated into feedthrough filter capacitor assemblies. The outer surface of the terminal pins is, in different portions of their longitudinal extension, provided with different coatings, i.e., metallization materials, such as, for example, titanium or similar metals, noble metals such as copper, carbon or combinations thereof, or braze materials like gold or silver. At one of the ends of the terminal pins, a Pd plated cap is bonded to the end surface of the pin by means of a laser spot weld.
In U.S. Publication No. 2011/0232961 of the Applicant, an electrical feedthrough for use in an electromedical implant is disclosed, which feedthrough contains terminal pins each of which has at least one section which can be jointed at a lower energy in the interior of the implant. Such pin section can, more specifically, be formed as a nailhead, which on its end face or in its entirety is wetted by a soft solder layer. The nailhead is implemented as a disc-shaped attachment which is soft soldered on the respective cylindrical pin body. The coating of the nailhead portion is made by dipping the pin end into a PbSn eutectic solder.
The present invention is directed toward overcoming one or more of the above-mentioned problems.